Association of sleep duration in middle and old age with incidence of dementia.
Sleep dysregulation is a feature of dementia but it remains unclear whether sleep duration prior to old age is associated with dementia incidence. Using data from 7959 participants of the Whitehall II study, we examined the association between sleep duration and incidence of dementia (521 diagnosed cases) using a 25-year follow-up. Here we report higher dementia risk associated with a sleep duration of six hours or less at age 50 and 60, compared with a normal (7 h) sleep duration, although this was imprecisely estimated for sleep duration at age 70 (hazard ratios (HR) 1.22 (95% confidence interval 1.01-1.48), 1.37 (1.10-1.72), and 1.24 (0.98-1.57), respectively). Persistent short sleep duration at age 50, 60, and 70 compared to persistent normal sleep duration was also associated with a 30% increased dementia risk independently of sociodemographic, behavioural, cardiometabolic, and mental health factors. These findings suggest that short sleep duration in midlife is associated with an increased risk of late-onset dementia.
Sabia 2021（Nature Communications, Whitehall II, n=7,959, 25年追跡）は中年期の睡眠不足と認知症の関連を決定づけた論文。50代で6時間以下の睡眠を続けた人は、7時間の人より認知症リスク30%増。70代まで持続的に短い睡眠の人ではさらに高い。
これが特に重い意味を持つのは、「短い睡眠は脳の老い方を変える」を示したこと。深い眠り中のグリンパティック系がアミロイドβをクリアする機序とも整合する。中年期の睡眠不足を「数年だけ」と軽く見ると、20年後にツケが回る。
外来で50代で「最近6時間しか寝ていない」と言う経営者には、必ずこの研究を共有している。「忙しいから後で」では遅い。今、睡眠を取り戻すことが、20年後の認知機能を守る最大の介入になる。